Balloons, gloves, inner tubes and silicone sheet as diaphragms — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/balloons-and-diaphragms/  (CC BY 4.0)
Basis: Measured thicknesses of common latex and silicone sheet sources; stretch limits from material data
Catalog version: 2026-10-20

Sizes: see table below
- Party balloon (latex, 12 in): 0.15–0.25 mm wall, stretches 600%; cut the neck off and use the flat 'equator' zone. Nitrile glove: 0.10 mm (palm), low stretch, best for low-pressure diaphragms under Ø40. Bicycle inner tube (butyl): 0.9–1.1 mm, stiff, fine for Ø80+ with 5 mm travel. Silicone sheet: 0.25 / 0.5 / 1.0 mm, survives 230 °C, the only one for a hot-side diaphragm.
- Sizing: a diaphragm's effective area is about the mean of the clamp bore and the centre disc; for the 12 oz can engine (Ø66 can, 10 mL syringe swept 2 mL) a Ø50 clamp bore with a Ø25 centre disc and 3 mm of travel gives about 4.4 cm² × 0.3 cm = 1.3 mL per direction. The clamp rings in the can-engine kit are Ø40, Ø50 and Ø60 bore.
- Clamp the sheet flat and slack (not pre-stretched) between two printed rings on six M3 screws; a smear of silicone grease on the lower ring seals it. Balloon rubber dies in sunlight in a few weeks; silicone lasts years.

material  thickness_mm  max_temp_c  stretch  use
12 in latex balloon  0.15–0.25  60  600%  cold-side diaphragm, Ø30–60
nitrile glove  0.1  80  300%  small low-pressure diaphragm
bicycle inner tube (butyl)  0.9–1.1  100  200%  large diaphragm, long travel
silicone sheet  0.25 / 0.5 / 1.0  230  400%  hot-side or long-life diaphragm
PE film (freezer bag)  0.05  70  low  displacer-rod seal only

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Diaphragm (mechanical device) — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Diaphragm_(mechanical_device)
- Wikipedia: Toy balloon — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Toy_balloon
- Long Earth Society: Engine builds (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/

Xem Studio scan: not needed; this is a published standard. The sheet is the geometry.
API: https://xemstudio.com/api/geometry?object=balloons-and-diaphragms